In my country it is a big business now, to sell "water structuring facilities". Promoters telling that after passing through them the water obtaining fantastic abilities basing on the fact that "water can keep information coded in molecular domains, chained by weak hydrogen bonds". This "structured" water is a panacea for all diseases.

I guess it is all started from this guy, but now they have a bunch of popular documentary films and many official academics supporting these ideas.

Which arguments should I use to convince my friends they're charlatans? I don't have a grade in physics, but from my basic university course I believe it is nonsense.

I think there must be some popular and simple facts that can be convincing enough for non-professionals who can understand physics at the high school level.

@Andrew: Even though it's true, that's not why the argument works, if it does. It works because it sounds scientific, and people want to be told what they should think.
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Mike DunlaveyNov 11 '11 at 19:13

It is not easy to convince someone who wants to believe otherwise. In my experience, no amount of detailed scientific information will help in this regard. People attracted to charlatans often interpret such arguments as "conspiracy of the scientific establishment".

However, seeing (or tasting) is believing, and what usually works well is experimental evidence. Make a double-blind test, where you let try your friends ordinary water and "structured water", and let them evaluate the difference (if any). Double-blind basically means, that neither the tester nor you (nor anyone else in the room) should know which is the "structured water" before the evaluation, to avoid some psychological bias. If you do sufficiently many of these tests (say, 20 probes for each type of water for 5 different persons, so 100 probes in total) you should get nearly a 50% chance that the tap water is identified incorrectly as "structured water" or vice versa. So if in the end only 40-60 of your probes are identified correctly your friends know that the structured water claim is bogus, since flipping coins to decide which water is which would have achieved the same result.

Beware, however, of slight temperature differences, particularly if the test consists in drinking the water. All physical and chemical conditions should be identical if you really want to test the (non-)effect of giving the water "structure".

At some fair the clever guys selling the structured water cooled it slightly below the tap water (about 1 Celsius less). Thus, the "structured water" tasted more fresh than the tap water.

As a historical aside, in Austria we have a similar issue with so-called Grander-water - funnily, Mr. Grander even received the Austrian cross of honor for scientific merits from former minister Gehrer. So even science ministers are not immune to such charlatans.

First step: Tell people that according to established physical theories there is no reason to believe that the claimed effect is true.

This does not prove anything, of course.

Second step: Ask them if they can detect the difference between processed water and not processed water in any way, if they can, for example "instantly feel" the difference.

If they say they can, propose a "double blindness test" where they get processed and not processed samples of water at random and have to tell you if their sample is processed or if it is not ("double blindness" is the word for word translation from German where neither the people who have to judge the water nor the people bringing them the water know which is which, I don't know the correct idiomatic translation). There are a lot of ways to cheat at such a test, of course. Try to do this in public and with the participation of uncorrupted scientists. There is of course the possibility that they can tell the difference based on an effect that is not related to the claimed properties of the water in any way, that is simply an insignificant side effect of the processing. There is no system and no procedure that saves you from falling into such a trap. Knowing that there can be correlation without causation is important, though.

Maybe they claim that the difference is only discernible on the long run. Ask for long-term, documented "double blindness" tests. Ask if these tests have resulted in statistically significant results. Run your own tests, if you must. If these prove the correctness of the claimed difference, accept it :-)

The worst thing is: sometimes the "structured" water has different taste. They gave me the water produced by that device and it has a taste of strong citric acid. I think the device injecting something into water to increase persuasiveness. And I don't have any friends-scientists. :(
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AndrewFeb 25 '11 at 20:29

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Ah, while writing my answer the answer above appeared :) @Tim van Beek: I think it is called "double-blind" test @Andrew: if the taste really is different then the water must be chemically or physically different, like in the temperature example in my answer. In that case it should be easy to find out, by measuring temperature, pH value or chemical composition. Temperature and pH value you can measure easily yourself.
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Daniel GrumillerFeb 25 '11 at 20:39

What is the most simple way to measure pH?
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AndrewFeb 25 '11 at 20:41

You put Litmus paper in the water and check the color.
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Daniel GrumillerFeb 25 '11 at 20:51

Another angle to consider here is investigation of these "water structuring facilities" themselves. I dont know whether one is dealing here with something mobile which is itself purchased for household use, or maybe for community use.

Either way I see that there are references in the comments to the water tasting different - citrus-like. This suggests:

(1) Does the machine use electrical power? If so what is powered: a traditional water-cooler powers the valve and fridge to cool the water. Does it have a powered motor?

(2) Does it overtly use extra materials? Thus does it need resupplying every so often with something? If so what?

(3) Does it covertly use extra materials? If it is bogus then it may have some filter material (which will eventually run out) which is supplying this extra taste.

If there is no obvious answer to the above, then try to identify what causes the taste difference. Is the water supplied separately (as happens with water coolers)? Also how is the water flowing through the machine?

As far as I know from friend's description: It uses electrical power. The device works in a coffee-machine style - user must fill it with water (about 5-10 liters) and turn it on. After 1-2 hours the "structured" water pouring out from 2 faucets, the first one is "aqua vitae" (the panacea for drinking), the second one is "water that helps to heal the wounds". Both "structured", taste is different.
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AndrewFeb 26 '11 at 20:32

There are electrodes inside and user must change them every 3-5 years. The main water tank is separated by some kind of membrane. Seems there are also magnets around tank, but they don't have direct contact with the water. No cooler or heatsink.
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AndrewFeb 26 '11 at 20:32